There may be an interesting economic lesson here: it really is not that easy to externalize costs. It surely can be done (air pollution), but it requires some special circumstances for those costs not to be internalized in a different form. (These special circumstances might include information asymmetries, harm to a public good, enjoyed by people other than a firm's own customers, etc.--themselves classic risk factors for market failure.)
By the same token, there probably are some truly externalized costs in this example, but I would expect them to be very minor and indirect. For example, most people probably do not pay the 'true' cost of their electricity. So to the extent electron wastes power, some of the cost will be internalized in the form of user dissatisfaction. But some will also be externalized either because the user doesn't know about the extra power consumption, or because the user herself doesn't fully internalize the costs of her power consumption and therefore doesn't care as much as she might if all costs were properly internalized.